Effects of thermal creep and high order slip/jump on natural convection in microchannels

Abstract

Natural convection gaseous slip flows in open-ended vertical parallel-plate microchannels with symmetric wall heat fluxes are numerically investigated. A second-order model, including thermal creep effects, is considered for velocity slip and temperature jump boundary conditions with variable thermo-physical properties. Simulations are performed for wide range of Rayleigh numbers from 5 × 10−6 to 5 × 10−3 in the continuum to slip flow regime. The developing and fully developed solutions are examined by solving the Navier-Stokes and energy equations using a control volume technique. It is found that the second order effects reduce the temperature jump and the slip velocity, whereas thermal creep strongly increases the slip velocity in both developing and fully developed regions. Moreover, the rarefaction effects increase the flow and heat transfer rates considerably.